Iphone 13Pro Max Stuck in Restore in Progress For Months!

I have tried everything! I started in early winter to use my IPhone. 13 Pro Max. It is stuck in Restore in Progress. Only 8.7 GB required to finish it. I have version ios15.2.1. I cannot shut down phone since back up is in progress. But it has been 3 months stuck! I have only 44.3GB of 512 GB used! So what is the problem? I have deleted every app I could to stop maybe app interference with the restore. I have plenty of ICloud storage too. How do I get this phone out of restore? I cannot sign out or shut down due to restore in progresse. I have had many iPhones. No problem at all with transferring and using them. This was a splurge. I am extremely disappointed.